In the handling of a string of casing, drill pipe or tubing, it is necessary to thread the pipe joints or sections together. As used in this disclosure, the term pipe joint will refer to one joint or length of drill pipe, commonly thirty feet in length. Many pipe systems comprise threaded pin and box connections. The pin and box connections thread together. The drill string is normally assembled so that rotation to the right (during the drilling process) tightens up the threads at the pin and box connections. They can become so tight that it is necessary to loosen then with power tongs. Hand powered tongs once were used on many rigs and are still sometimes available but the power tongs have partially replaced them. They can also become so tight that it is necessary to supply a controlled amount of torque to the threaded joint to make the disconnection. In like fashion, it is necessary to tighten the threads controllably when making up the string of pipe. While this is common in a drill string, it is also necessary in the event of threading several sections of pipe together to form a casing string. While the size of the pipe may differ, and the threads may differ in some detail, all of these procedures require controlled threading and unthreading. Controlled threading and unthreading must be done simultaneously while supporting the string of casing or the drill pipe hanging below the surface. In fact, several tons of pipe comprising several thousand feet of pipe may be suspended below the drilling rig rotary table. This is normally rested in the rotary table. The rotary table is equipped with a central opening. This opening is normally a rectangular opening to engage the kelly which is stabbed through the opening so that the rectangular opening engages the external profile of the kelly to impart torque to the pipe string. Sometimes, however, that opening is replaced with a different kind of opening which is known as a bowl and the bowl is partially blocked up with a set of slips (usually several slips) which collaborate to grab a pipe extending through the bowl.
The bowl is larger than the pipe, but the space between the bowl and the pipe adjacent to it is filled by the wedge shaped slips. Moreover, the slips are positioned to encircle a pipe and clamp against the joint. The coupling defines a thicker pipe length between the spaced shoulders where the downwardly facing shoulder is secured above the bowl. While several thousand feet of pipe will hang below the bowl, the open upper end of the pipe string enables threading at that location.
In times past, roughnecks on the rig floor have used a set of tongs to grab the pipe, grip the pipe and make or unmake a threaded joint. With a long drill string suspended in the well borehole, and with all the weight that is on it, it is often possible to count on the massive inertia of that weighty string of pipe to prevent unintended rotation when threading or unthreading a joint of pipe. With a typical set of elevators, the next joint of pipe is removed from the mouse hole, suspended in the derrick and stabbed into the top most open end of the pipe string using a set of tongs to rotate this pipe joint (weighing perhaps 600 pounds) to be threaded to the pipe string which may weigh 100 times greater. That is an acceptable procedure.
All the procedures which have been used heretofore have featured spinning chains, perhaps fifty years ago, and pipe spinners, perhaps thirty years ago and power tongs which have replaced the spinning chains and which are intrinsically safer. There are occasions in which first and second power tongs are used together. One set of tongs will grasp and hold the pipe above the threaded connection while the lower set of "tongs" will grasp and hold the pipe joint for that connection. In that instance, one of the power tongs will rotate while the lower unit will simply grasp and hold the pipe. The latter tongs are commonly called the backup tong. Since the upper tong is powered, the other tong simply provides a stationary grip on the pipe, fixing it so that it holds still while rotation is applied on the other side of the threaded joint.
A good deal of coordination is required to work two sets of pipe equipment, commonly the power tong and the backup (more or less equal in weight and size). Moreover, these two "tongs" typically are so large and heavy that they have to be suspended from some sort of overhead chain or pivot to enable service personnel on the rig floor to handle them. The workmen (known as roughnecks) are engaged in a dangerous enterprise when they have to grab or wrestle a chain suspended set of tongs, move them over towards the center line position (defined by the rotary table) and then position the power tongs for grasping the pipe. This problem is true both for light weight hand operated tongs as well as motorized tong systems. It is twice the problem if there are two sets of tongs. Partly, the two sets of tongs must be moved in a synchronized fashion to engage and grasp the pipe string. When that is done the coordination is difficult, the work is hard, the risk is increased, and operator errors become more commonplace. The power tong units weigh several hundred pounds. When there are two of them, it is possible to suspend the bottom "tongs" from the upper tong. That leaves the personnel on the rig floor moving a different amount of weight which is troublesome in the extreme. The weight that must be handled poses a good deal of struggle which, in the best of circumstances is hard and difficult work. In the worst of circumstances, the floor is wet and slick, the pipe may be crooked or bent, and the amount of torque required from the tong will vary from joint to joint. Also, there is always the human operator problem, namely that the threaded joint may be stopped about 20 inches above the rotary table, and then the next occasion may involve stopping 40 inches above the rotary table. Because this height will vary, the tongs have to be engaged with the pipe at different heights, and that requires vertical movement as well as lateral movement to bring the tongs into operative position.
There is a coordination requirement between tong movement and installation of the slips in the bowl. The physical location of these jobs poses something dangerous to nearby personnel. It is easy to get a hand or arm pinched, and it is not unusual to see roughnecks missing one or two fingers. It is even a little bit more difficult if it is done aboard a drill vessel which may rise and fall with wave action, as for example in a semisubmerssible rig. All these factors create difficulties.
In one aspect, the present invention is an improvement over a pair of independent, suspended power tongs in a drilling rig. Without belaboring the point, the roughnecks must maneuver both sets of tongs so that they are aligned with the pipe notwithstanding the height of the pipe extending above the slips and bowl, and must do this with both straight and crooked pipe.
The present disclosure reduces the weight and heft of this system by anchoring the lower tong (below, it is called the backup mechanism) on a platform which surrounds the bowl, and which incorporates the appropriate slips which are stabbed into the opening. The suspended weight is reduced more or less by 50% by doing this. If each set of tongs weighs 400 pounds, this is a sizable reduction is the movable weight. Moreover, it locates the HB system in alignment with the slips and rotary bowl. In the present disclosure, a framework sits near and in alignment with the bowl. It supports a set of slips which are mechanized for insertion into the bowl. All of this is located on a framework having the shape of a donut with the bottom plate bearing against the rotary table and with the top plate elevated thereabove. The top plate pivotally supports a set of slips. This enables the slips to be easily positioned. Above and in axial alignment, the lower H B assembly is supported on the framework. The lower tong assembly is optionally raised or lowered. The H B is anchored on the frame and therefore it is not a heavy item to be forced into the axial pathway of the pipe. It is located at that location so that it can reach out and grab the pipe below the coupling to enable the pipe to be engaged with the bowl and slips.
The present disclosure sets out the HB mechanism which is self aligning with respect to the pipe. It reaches out to grab and hold the pipe notwithstanding movement of the pipe to the left or right. The range of reach is adjustable so that it can accommodate relative movements. The lower assembly accomplishes hydraulic alignment below the coupling. This is on a tubing spider which is installed on the rotary table. Effectively, through the use of an automated power tong thereabove, it provides greater speed going in or out of hole. It can be done with a large casing, standard size drill pipe and even with small tubing such as will be installed during a well completion process. Better than that, it can be operated somewhat remotely so that the personnel do not have to get into the limited floor area between the four legs of the derrick. This cuts down on crowding. This also permits a reduction of personnel in that vicinity so that there are fewer people exposed to the danger. This is equipment that can be conveniently used to provide control threaded torque in making or breaking a threaded joint. This especially is effective as a backup tong and also as a moveable pipe clamp mechanism. It can be used on equipment located on land or sea. It is effective also to accomplish clamping, thereby securing the pipe against any unintended movement at or during threading operations.